1. Technical Field
Various embodiments of the inventive concept relate to a semiconductor integrated circuit, and more particularly, to a semiconductor memory apparatus and a temperature control method thereof.
2. Related Art
With demands in low power semiconductor memory devices, next generation semiconductor memory devices with non-volatility and non-memory refresh have been researched. A phase-change random access memory device (PCRAM) which is one of the next generation semiconductor memory devices, stores data using a resistance difference between an amorphous state and a crystalline state of a phase-change material. The phase-change material changes between the amorphous state and the crystalline state by an electrical pulse applied thereto.
Germanium (Ga)—antimony (Sb)—tellurium (Te)—based material (hereinafter, referred to as GST), which is a chalcogenide, has been most widely used as a phase-change material of a general PCRAM. This is because the GST material has a fast phase-change rate and good oxidation resistance and is stable.
The GST material has a characteristic that its resistance value is changed under an effect of an external temperature. In other words, the resistance of the GST material is reduced in a high temperature and increased in a low temperature, regardless of phase-change.
Thus, when the resistance of the GST material is measured by applying a certain voltage regardless of a temperature of the GST material, a measured resistance value of the GST material is different depending on temperature change. Specifically, in a multi-level cell, resistance values of multi-levels may not be accurately distinguished and thus a data error occurs.